Chapter 9 - Energy and the Cell
NEW AIM: Describe the process and purpose of cell resp.
Breathing (respiration)
and
Cellular Respiration
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell resp.
(respiration)
Fig. 6.1
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell resp.
1. We breathe to take in O2 (oxygen has second highest electronegativity next to fluorine)
2. Electrons (and protons) are passed from glucose to O2 (exergonic).
i. O2 becomes H2O
ii. Glucose become CO2
3. The KE of the moving electrons is used to power ATP synthase, the enzyme that adds a
phosphate to ADP (endergonic). Steps 2 and 3 are cell respiration.
4. The CO2 is a waste product, you breathe it out (excretion). The water may also be a waste
product if you have enough water – breathe it out, sweat (excretion)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
We only capture ~40% of the energy stored in glucose as ATP. The rest is lost as heat
and light (2nd law of thermodynamics). Cars are much worse.
Fig. 6.2
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
75%
About 75% of the ATP we make just goes into
housekeeping (maintaining order: protein
synthesis, DNA synthesis, RNA synthesis,
breathing, heart beating, etc…)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
25%
Only 25% goes into all the voluntary
activities like walking, running,
thinking, eating, etc…
Table 6.3
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What is a calorie (cal) or Joule (J)?
1. Unit of energy in English and metric system, respectively
2. One calorie = 4.184 J
3. A calorie (or 4.184 J) is the amount of energy required
to heat: 1 gram (1ml) of water by 1°C
4. A food calorie (calories listed on food labels) is really a
kcal (kilocalorie) or 1000 calories
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
It is really 90,000 calories per
serving, but that would just be
too scary so we divide by
1000…
4. A food calorie (calories listed on food labels) is really a
kcal (kilocalorie) or 1000 calories
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
It takes ~7.3 kcal to make a
mole of ATP. The average adult
requires 2200 kcal/day. How
many ATP can be made from
this?
120.5 moles
(don’t forget to account for the inefficiency of cell resp - lose
60% of the energy to heat and light)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What do cells do with glucose?
1. Burned (combustion) to CO2 and H2O, energy transferred to ATP
2. Biosynthesis, make other organic molecules like amino acids,
triglycerides, etc…
3. Stored as glycogen or triglycerides
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
1. Glucose can be “burned” controllably by enzymes as electrons (and protons) are passed to O2
(highly electronegative O – pulls electrons away from C-C and C-H) – exergonic (-ΔG) overall.
2. O2 will become H2O upon being reduced - gaining electrons (and protons follow).
3. Glucose will be oxidized to CO2 upon losing the electrons (protons follow).
4. KE of moving electrons powers enzyme (ATP synthase) to perform dehydration synthesis and put
a phosphate on ADP making ATP (endergonic reaction(+ΔG)).
5. 36 ATP per glucose, 60% KE of electrons lost to heat and light (hit other things as they are
transferred).
Fig 6.4
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Oxidation
vs
Reduction
(Redox Reactions)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Oxidation
- To lose electrons (oxygen steals them and therefore
you have been oxidized).
Reduction
- To gain electrons
Something cannot lose electrons without something else gaining them.
Therefore, they go together and are called redox (reduction-oxidation
reactions).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Redox reactions
Electrons (H+ follow)
Electrons (H+ follow)
In the above reaction, what substance has been oxidized
and what substance has been reduced?
Glucose loses electrons to O2 and therefore glucose is oxidized to CO2,
while O2 is reduced to H2O.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Redox reactions
Electrons (H+ follow)
Electrons (H+ follow)
In the above reaction, what substance is the reducing
agent and what is the oxidizing agent?
The reducing agent does the reducing (gives the electrons) and therefore is the one getting oxidized = glucose
The oxidizing agent takes the electrons and is therefore being reduced = O2
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Redox reactions
Figure 9.3 – methane combustion
(combustion = exothermic oxidation reaction – burning a fuel)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The reduction of NAD+
Here, NAD+ has been reduced to
NADH (it gained electrons). Notice
the extra hydrogen on the top of
the nicotinamide ring in blue
representing 2e- and one H+.
NAD is an electron shuttle – brings
electrons from place to place like a
bus bringing people around.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The reduction of NAD+
In the above reations, who is oxidized and who is reduced?
The molecule with the hydroxyl (malate) has been oxidized to the
molecule with the carbonyl (oxaloacetate), while NAD+ has been
reduced to NADH.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The reduction of NAD+
Who has the higher affinity for electrons, malate or NAD+?
Obviously NAD+ has the higher affinity otherwise the electrons would not move thereby
making it an endergonic reation.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The reduction of NAD+
Is this reaction exer- or endergonic?
It must be exergonic as there is no input of energy from the outside.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Questions
1. Identify three ways by which a protein can be activated.
2. What is a kinase?
3. There are two major types or classes of receptors that cells have evolved to use.
What are they?
4. When a single ligand binding event to a membrane receptor triggers the downstream
activation of 100’s or even 1000’s of transcription factors, this is known as…
5. a. Tetracycline works by interfering with the function of the _______________.
b. This is a great drug target because…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Cell Respiration (general OVERVIEW)
1. Glucose will be stripped on its electrons (oxidized) and the electrons will be given to
NAD+ and FAD (reduced) in the cytoplasm and matrix of mitochondria.
Both NAD and FAD have a higher affinity for electrons than glucose and its byproducts.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Cell Respiration (general)
2. NADH/FADH2 will then pass the electrons off to an ETC (electron transport chain; a
series of redox reactions) located in the inner mitochondrial membrane for cell resp. – a
chain of proteins and other non-protein electron carrier molecules that will pass the
electrons from low to high affinity (next slide)…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Cell Respiration (general)
3. The KE of the moving electrons is transferred to the proteins of the ETC to power
them (get them to move). These proteins are active transport pumps - specifically
proton (H+) pumps, which pump H+ into the inter membrane space generating an H+
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.6A
Series of redox reactions (ETC)
?
4. Waiting at the end of the ETC in the matrix is O2, which is reduced
to H2O and a new O2 comes in and so on... What would happen if
there was no O2 there?
The electron carriers would have nobody to give their electrons to and the flow of
electrons would STOP! No KE! Proton pumps do not work = death
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.6A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The two mechanisms
by which ATP is generated
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
1. Substrate-Level phosphorylation
ADP is phosphorylated by an
enzyme using a substrate that has a
phosphate the REALLY doesn’t want
to be there (VERY low affinity). It
has a higher affinity for ADP! This
substrate is HIGH ENERGY.
Fig. 6.7B
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
2. Oxidative phosphorylation
ADP is phosphorylated by ATP
synthase, which is powered by the
OXIDATION of glucose – moving
electrons.
Fig. 6.7A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
2. Oxidative phosphorylation
Remember the ETC and those protons pumps,
well they pump protons across a membrane
from low to high concentration (active
transport - endergonic) using the KE of the
moving electrons (exergonic) – energy
coupling. This forms a proton concentration
gradient…
Fig. 6.7A
The protons then passively diffuse through
ATP synthase (facilitated diffusion) – known
as CHEMIOSMOSIS (= the diffusion of ions
like H+) across a membrane down their
electrochemical gradient. The KE of the
moving protons is transferred to ATP
synthase so it can put a phosphate onto ADP
to make ATP.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
2. Oxidative phosphorylation
Electrochemical gradient
This proton gradient is not just a chemical
gradient, but an electrochemical gradient.
Why the electro- prefix?
Fig. 6.7A
Electro- for electromagnetic force. The two
side of the membrane have different charges.
Why?
Protons (H+) are positive. If you pump lots
of positive to one side, this side is more
positive than the other side. Therefore, the
protons are pushed by the EM force away
from this side towards the other side of the
membrane, which is less positive (relatively
negative).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
2. Oxidative phosphorylation
Electrochemical gradient
These are more powerful (store more PE)
than just chemical gradients. Why?
Because of the additional EM force pulling
them across, not just random motion and
probability (diffusion).
Fig. 6.7A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
BRIEF Recap
1. Electrons stripped from glucose and given to NAD+ and FAD to make NADH and FADH2
in cytosol and matrix (exergonic).
2. NADH and FADH2 give electrons to mitochondrial ETC on inner mito membrane (exergonic).
3. Electrons are passed down ETC from low to high affinity and in the end O2 in the
matrix, which is reduce to H2O and goes on its merry way (exergonic).
4. KE of moving electrons through ETC powers active transport of H+ from matrix to inter
membrane space generating an H+ gradient (endergonic).
5. H+ facilitatively diffuses back to matrix through ATP synthase (exergonic).
6. ATP synthase uses KE of moving protons (exergonic) to put phosphate on ATP
(endergonic). There you go, energy from glucose into ATP…
There are 1000’s of ETC’s and ATP synthases in the inner mito membrane, hence the high
surface area thanks to the cristae, so that much ATP can be made per second…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Cellular Respiration - detailed
(broken into three stages)
stage
Location where it occurs
1. Glycolysis
cytosol
2. Krebs Cycle / TriCarboxylic Acid (TCA) cycle / citric acid cycle matrix of mito
3. ETC
inner mito membrane
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Questions
1. Identify the two general methods by which ATP is generated
during cellular respiration.
2. List the four general divisions of cellular respiration.
3. Define chemiosmosis.
4. What cellular respiration protein complex is involved in
chemiosmosis?
5. Electrons are brought to the ETC by what two molecules (which
are also cofactors)?
6. Write down the overall reaction of glycolysis.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.8
Overview of the three stages of cell resp. and where they happen…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
(Fermentation)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Always keep in mind the goal. What is the goal of cellular respiration?
To take the electrons from glucose and pass them to oxygen, using the KE of the
electrons to make ATP.
Then let’s start taking those electrons…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
1. Glucose will first be split into 2 pyruvate molecules via glycolysis in the cytosol. A bit
of ATP is made (substrate-level) and some electrons stripped (handed off to NAD+).
2. The 2 pyruvates will then enter the mitochondria and will be fed into the Kreb’s cycle,
which will strip down the remainder of the accessible electrons leaving CO2 behind. NAD+
and FAD will take the electrons to the ETC.
3. NADH and FADH2 drop electrons off to ETC, protons are pumped into inter membrane
space and diffuse back through ATP synthase making ATP (oxidative phosphorylation).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Let’s start from the beginning:
How does glucose enter the cell?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What style of transport protein is Glut-1? Facilitated diffusion, carrier protein
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Glucose enters by facilitated diffusion (it is typically higher in concentration outside the cell)
through GluT1 (glucose transporter-1). Once inside the cell it MIGHT enter glycolysis.
Obviously, let’s say it does…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Glycolysis
What does glyco- mean? Sugar
and lysis? splitting
Glycolysis = sugar splitting
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Glycolysis – overall reaction:
These molecules are simplified only showing the carbons. Obviously,
this is not the molecular structure of glucose, just the carbons.
Fig. 6.9A
Glycolysis
Glycolysis is an enzyme pathway
consisting of nine steps (nine
enzymes).
Remember, it is like a factory
line where the product of
enzyme 1 is the substrate for
enzyme 2, etc… and the
molecule gets modified a little
bit in each step.
Fig. 6.9B
Glycolysis
Intermediates
Substances that are both substrates and
products. For example, glucose-6phosphate is the product of enzyme 1
(hexokinase) and the substrate for
enzyme 2. Therefore it is an
intermediate (only around for a short
time in between the substrate glucose
and the end products – 2 pyruvates).
Fig. 6.9B
Glycolysis
In the end, 2 pyruvate are
formed (3-carbons each) from
the splitting of one glucose (6carbons)
Fig. 6.9B
Glycolysis
Red sphere indicate enzymes.
The substrates/products are
written out in words.
Glycolysis is broken into two
phases:
1. Preparatory phase (steps 1-4)
This phases uses 2ATP (say
what??). Think of it like the
activation energy needed to get
the entire process rolling.
2. Energy payoff phase (steps 5-9)
This phase, as its name
implies, is where 4ATP are
made (2 per pyruvate) and 2
NADH are formed from 2 NAD+
(redox reaction).
Step one is the endergonic reaction catalyzed by our old friend hexokinase, made
possible by energy coupling to the hydrolysis of ATP.
Q. Why doesn’t the cell reach equilibrium with the glucose concentration outside
resulting in a net flow of zero glucose across the membrane?
A. Glucose is converted to glucose-6-phosphate thereby lowering the glucose
concentration in the cell. Glucose-6-phosphate cannot pass through GLUT1 making zero
probability of it leaving the cell.
Fig. 6.9B
(in cytoplasm)
What does adding those two phosphates do?
This energy transfer will destabilize the molecule so that enzyme 4 will be able to split
it into two into two G3P (glyceraldehyde-3-phosphate).
Fig. 6.9B
(in cytoplasm)
ENERGY PAYOFF PHASE
Step 5 is a REDOX reaction where NAD+ is reduced and G3P (glyceraldehyde-3phosphate; also known as PGAL (3-phosphoglyceraldehyde)) is oxidized.
***It is VERY important to realize that in step 4, the 6-carbon fructose was SPLIT into
two 3-carbon G3P’s. Each G3P will go through steps 5 through 9. The numbers shown
in this figure are for both G3P’s. For example, G3P is oxidized as one NAD+ is reduced
to NADH. The figure says 2NADH, one for each G3P.
(in cytoplasm)
G3P (glyceraldehyde-3-P) = PGAL (3-phosphoglycerate)
ENERGY PAYOFF PHASE
Steps 6 through 9
- further rearrange the atoms
while pulling off the phosphates
and making 4 ATP. Two per G3P.
- End products are two pyruvates
Fig. 6.9B
(in cytoplasm)
GLYCOLYSIS
In detail showing the enzymes and actual
substrates/products/intermediates
Glucose is well on the way to being
stripped of all its available electrons and
becoming CO2
(in cytoplasm)
Glycolysis
What is the net payoff?
2 ATP and 2 NADH formed
How many electrons were
stripped from glucose thus far?
4, 2 per NAD+
Where do the ATP go?
ATP diffuses around in the
cytosol and is used to power
endergonic reactions of
course…
Where do the NADH go?
NADH goes into the matrix and
drops the electrons off to the
ETC and the proton falls off
into the matrix.
Glycolysis
How many NADH are made per
G3P?
1, remember that two G3P
molecules are going through
steps 5 through 9 and so the
numbers are doubled.
How many ATP are made per
G3P?
2, one at step 6 and one at step 9.
Where are the pyruvates off to?
The pyruvates will now enter the
mitochondrial matrix via facilitated
diffusion to be stripped naked of
the rest of its loose electrons
(oxidized).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The pyruvates are off to the Krebs cycle (the dance), but you can’t go to the dance before
you are GROOMED!!! Pyruvates enter the mitochondrial matrix via facilitated diffusion or
active transport (depends on organism / cell).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Grooming of pyruvate in preparation for the dance:
Fig. 9.10
ATP COST:
Depending on the concentration gradient, it could cost one ATP per pyruvate during active transport
across the mitochondrial membrane.
(Mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Grooming of pyruvate in preparation for the dance:
Fig. 9.10
Before entering the Krebs cycle, pyruvate is groomed (modified). It gets a “haircut” as electrons
are removed and passed to NAD+ (redox) and a CO2 is cut (decarboxylation) – this is the first
carbon lost and you will breathe it out – excretion. The result is an acetyl (2-carbon molecule).
The acetyl is too young and must be escorted to the dance by Coenzyme A (CoA; as the name
implies, is a cofactor made from vitamin B5) resulting in Acetyl-CoA (two per glucose). They are
now ready for the dance (Krebs cycle/TCA cycle).
These reactions are catalyzed by the pyruvate dehydrogenase complex (Mitochondrial
matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Grooming of pyruvate in preparation for the dance:
Fig. 9.10
Acetyl group
(memorize it)
The acetyl has a higher affinity for the CoA relative to the carboxyl group highlighted in blue. Therefore this is
exergonic (-ΔG) and the acetyl transfers to CoA. This must happen because if water if water were to hydrolyze
off the CO2 instead of CoA, the acetyl would not leave oxygen and jump onto OAA in Krebs. The squiggly line
shown in acetyl CoA means a high energy bond or that the acetyl is not held tightly. If instead the CoA were
(Mitochondrial matrix)
–OH, the acetyl is then attached to O and would not go to OAA.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Grooming of pyruvate in preparation for the dance:
Look at the acetyl. How many electrons remain that can be grabbed by NAD+/FAD?
You should see 8 electrons held between C-C and C-H.
(Mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
CoA is made using a phosphyorylated ADP, the ESSENTIAL (meaning you can’t synthesize
it) vitamin pantothenate (Vit B5) and a molecule called β-mercaptoethylamine, which is
made using the amino acid Cysteine.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Acetyl
Coenzyme A (CoA)
= thioester
Acetyl CoA
Look at the thioester (thio = sulfur;
ester with sulfur instead of oxygen) that
forms. This attachment is unstable.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
A violent dance (more like a
furnace) where the remaining
low affinity electrons are
stripped from the acetyl leaving
behind two CO2 (“the bones of
glucose”). Basically, the acetyl
is burned (combustion)!
Fig. 6.11A
(In mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Figure 9.11 from textbook
showing both Grooming and the
Kreb cycle (citric acid cycle /
tricarboxylic acid cycle).
Fig. 9.11
(In mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
How many cycles occur
per glucose?
CoA escorts the acetyl to
the dance and goes back to
get another…
2, since one glucose becomes 2 pyr,
which are groomed to 2 acetyl-CoA
This figure shows only ONE cycle.
Fig. 6.11A
(In mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.8
Overview of the three stages of cell resp. and where they happen…
Fig. 9.12
KREBS CYCLE
As always, metabolism is like a factory line
as each step is a small change catalyzed by a
separate enzyme represented by blue
numbered spheres in the figure.
In step one, enzyme 1 catalyzes the transfer
of the acetyl from CoA to OAA (oxaloacetate
– 4 carbons) resulting in the formation of
citrate – 6 carbons (hence the citric acid
cycle).
OAA has a higher affinity for acetyl than CoA
and the transfer is therefore exergonic.
How many carboxyl groups on citrate?
3, hence tricarboxylic acid (TCA) cycle
(In mitochondrial matrix)
Fig. 9.12
KREBS CYCLE
Let the burning of the acetyl begin.
Low affinity electrons are being
stripped catalyzed by enzyme 3 and
enzyme 4, both of which are
dehydrogenases (redox and
decarboxylation).
You can see the skeletal remains of
glucose as the two CO2 molecules are
spit out. You will excrete these.
Where are the NADH going?
To drop off electrons at the ETC
(In mitochondrial matrix)
Fig. 9.12
KREBS CYCLE
Enzyme 5 catalyzes substrate level
phosphorylation first of GDP to GTP.
The phosphate on GTP is then
transferred to ADP to make ATP (just
bouncing a phosphate around).
Enzyme 6 catalyzes another redox, but
his time FAD is reduced to FADH2, also
going to the ETC.
(In mitochondrial matrix)
Fig. 9.12
KREBS CYCLE
Enzyme 8 catalyzes then final redox
reaction and NAD is once again reduced
to NADH and the product is OAA – back
to the beginning (cycle).
How many electrons have been stolen
from the acetyl?
8, just as you predicted earlier
How many carbons are lost from the
cycle as CO2?
2, just as you predicted earlier
(In mitochondrial matrix)
Fig. 9.12
KREBS CYCLE
Follow the carbons…
How many carbons enter the cycle?
2 per acetyl
How many carbons leave the cycle as
CO2? This should then also be 2 since you
strip all available electrons from the
acetyl leaving behind the “bones” or
CO2.
The carbons are color-coded for you to
follow. Follow the carbons that enter
and look at which ones leave. What do
you notice?
The acetyl carbons are not the ones being lost initally. Two
other carbons are lost. They will eventually become CO2,
but it make take a few turns. But what does it matter which
carbons exit? It doesn’t.
(In mitochondrial matrix)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Where does the ATP go?
Out of the mitochondria to be
coupled to endergonic
reactions like active
transport, anabolic reactions,
etc…
Where do the NADH and FADH2
go?
To drop off their electrons to
the ETC and come back to get
more (you realize when I say
come back I mean randomly
diffuse back).
How many NADH/FADH2/ATP
are made per acetyl?
Per glucose?
Per acetyl you make 3NADH, 1FADH2 and 1ATP.
Glucose yields two acetyl and therefore you make 6NADH,
2FADH2 and 2ATP.
Detailed Krebs Cycle
(enzyme names)
As expected, all the enzymes
reducing NAD+ and FAD are
dehydrogenases (removing
hydrogen and of course the
more important electrons).
What do you notice about all
the enzymes ending in
“dehydrogenase”?
They all perform redox reactions and
therefore remove hydrogens when the
electrons are taken.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Off to the ETC…
It is now time to follow the only trace
remaining of the original glucose, the
electrons (and protons) being carried by
NADH and FADH2 coming from glycolysis,
grooming and the Krebs cycle…It is off to
the ETC!!!
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Questions
1. Write down the overall reaction of glycolysis.
2. How many ATP are formed during glycolysis?
3. Glycolysis is broken up into two halves. These are known as…
4. During grooming, a CO2 molecule is released. This process of removing a CO2 from
pyruvate is known as_______________________.
5. The major regulatory step of glycolysis and cell respiration for that matter occurs at
what enzyme?
6. In terms of cellular respiration, the main objective of the Krebs cycle, and the reason
some refer to it as a furnace, is to…
7. All the NADH and FADH2 bring their electrons to _________________.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Overview figure for studying…
Fig. 9.16
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
The ETC and ATP synthase:
Fig. 9.15
1. The mitochondrial ETC (electron transport chain) is found in the inner
mitochondrial membrane
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
2. It consists of three integral membrane proton pumps (protein complexes I, III and
IV), one non-protein electron carriers (Q) and one protein electron carrier (cyt c),
which carry electrons between the pumps, and integral membrane protein complex II,
which takes electrons from FADH2. Complex II is NOT a proton pump.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
Q = ubiquinone (Coenzyme Q10)
An oil soluble electron shuttle located
within the inner mitochondrial
membrane that carries 2 electrons at a
time from complex I and complex II to
complex III.
Food for thought: We are able to synthesize ubiquinone using multiple acetyl CoA. The enzyme
HMG-CoA reductase is involved. Where have we seen this enzyme before and why might this cause
alarm?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
Cytochrome c (cyt c)
Cytochrome c (cyt c) is a small heme (cofactor/coenzyme; and you thought hemoglobin was the only protein
that used the heme cofactor…) containing protein. It does NOT bind oxygen though. It is a peripheral
membrane protein that carries one electron at a time from complex III to complex IV. YES, HEME CAN ALSO ACT
AS AN ELECTRON CARRIER!!!!
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
What can you say about the electron affinity of each pump and carrier as the electrons move
from NADH/FADH2 toward oxygen?
The affinity for the electrons increases…they are being held more and more tightly.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
Describe the flow of electrons from NADH
3.NADH drops off its electrons to the first proton pump (complex I), which passes the electrons to
ubiquinone, which brings them to the second proton pump (complex II), which passes them to cytochrome c,
which passes one at a time to complex IV, which finally passes them to O2, which gets reduced to H2O. These
are ALL redox reactions…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
5. What is the point of moving the electrons?
The KE of the moving electrons (exergonic) is used to power the proton pumps to actively transport protons (H+) from
the matrix to the intermembrane space (endergonic) resulting in an electrochemical gradient. The pumps will pump
one proton for every electron that moves through them.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many electrons are being pumped per NADH?
The pumps will pump one proton for every electron that moves through them. Therefore, when NADH drops off two
electrons to complex I, two protons will be pumped. Then when the 2 electrons get to complex III, 2 more will be
pumped and the same with complex IV. In the end, 6 protons are pumped be NADH.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many electrons are being pumped per FADH2?
FADH2 holds its electrons more tightly than NADH and complex I is not strong enough to grab them away. Therefore
FADH2 drops its electrons off at complex II, bypassing complex I. Since the 2 electrons will only pass through proton
pumps III and IV, only 4 protons will be pumped resulting in less ATP being made per FADH2 compared to NADH.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
What type of gradient is generated by all of this proton pumping?
electrochemical gradient – a gradient not only based on chemical concentration, but on charge as well. When the positive
protons are pumped into the intermembrane space, the matrix becomes negative relative to the intermembrane space.
Therefore the protons move back to the matrix because of gradient and charge (they are positive, matrix is relatively
negative).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
What is the point of pumping the protons into the intermembrane space?
The protons will only be allowed to diffuse (chemiosmosis = the diffusion of any ion across a membrane whether it be H+,
Na+, Cl-, etc…) back down the electrochemical gradient through ATP synthases (facilitated diffusion). The KE of the
moving protons (proton motive force) (exergonic) is used to power and spin ATP synthase, which pushes a phosphate onto
ADP (endergonic; phosphorylation of ADP) = energy coupling.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many NADH/FADH2 bring electrons to the ETC per glucose?
10 NADH (2 from glycolysis, 2 from gooming and 6 from Krebs) and 2 FADH2 (from Krebs) = 24 electrons
What happens to NAD+ and FAD after dropping off the electrons?
They return to glycolysis, Grooming, Krebs to get more electrons (and protons)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many ATP are made per glucose by oxidative phosphorylation?
~38 are made in total, but 4 are made by substrate level in glycolysis and Krebs leaving 34 made by
oxidative phosphorylation.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many ATP are made per NADH/FADH2? (remember that FADH2 will make fewer)
Since 10 NADH and 2 FADH2 deliver electrons per 34 ATP, each NADH makes ~3ATP and
each FADH2 makes ~2 ATP.
Fig. 9.15
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.15
How many protons need to diffuse through ATP synthase to make one ATP?
You should be able to figure this out without memorizing. Since each NADH (2 electrons) resulting in the
pumping of 6 protons and makes 3 ATP, you must need 2 protons to make an ATP. Likewise, FAD only pumps
4 protons and therefore only 2 ATP are made.
2 protons for 1 ATP
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Questions
1. NADH gives its electrons to _________________, which has a _____________
affinity for them making this reaction, in terms of energetics, _________________.
2. In contrast, FADH2 gives its two electrons to…
3. Why does FADH2 not also give its electrons to the same entity as NADH?
4. The movement of electrons from NADH to oxygen is used to generate a…
5. Identify the two examples of energy coupling during oxidative phosphorylation.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Free Energy Change along the ETC
As you would expect, the amount of free energy drops as
the electrons move from low affinity to high affinity and in
the end to oxygen, the final electron acceptor.
All of the protein complexes use cofactors to transport
electrons. Amino acids cannot efficiently transfer electrons
around.
Fig. 9.13
NADH Dehydrogenase (Complex I)
4Fe-4S cluster x 7
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What would happen in the absence of Oxygen?
Without molecular oxygen (if you didn’t breathe) the electrons would get stuck in the
proton pumps and carriers (it would get clogged). No protons would be pumped and
therefore no ATP would be made…death.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Let’s look at some chemicals that poison the ETC.
Fig. 6.13
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Overview figure for studying…
Fig. 9.16
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Chemiosomotic phosphorylation
is synonymous with
Oxidative Phosphorylation
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Thus far we have been discussing aerobic
respiration, which is cellular respiration using
oxygen as the final electron acceptor…
What about organisms or cells that can live in the
absence of oxygen like yeast, many bacterial
species and even your own muscle cells at times?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
NEW AIM: How do cells make ATP in the absence of O2?
Aerobes
organisms/cells that require oxygen to perform cell respiration
(aerobic respiration) to make ATP and thrive
Anaerobes
organisms/cells that do not require oxygen for growth and may even
die if placed in the presence of oxygen
1. Strict (obligate) Anaerobes
2. Facultative anaerobes
Chapter 9 - Cell Resp: Harvesting Chemical Energy
NEW AIM: How do cells make ATP in the absence of O2?
Strict (obligate) Anaerobes
- Cannot function in the presence of O2 (Oxygen is
highly poisonous without the proper enzymes to deal will the
undesirable oxidation of molecules like your DNA - disorder)
- They still use Krebs and ETC. WHAT!? How is that possible?
- Easy, they just need a different, albeit weaker (less oxidizing) final
electron acceptor instead of O2, like sulfate (anaerobic respiration).
- Sulfate (SO4) is reduced to H2S (rotten egg smell!)
- All such organisms are prokaryotic
Chapter 9 - Cell Resp: Harvesting Chemical Energy
NEW AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
- An organism that can make ATP using O2 if present
(aerobic respiration), but can switch to fermentation
to make ATP if O2 is not present.
- Typically many bacteria, but our muscle cells can also do this
as well as certain fungi like yeast (single-celled fungus)
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
Aerobic respiration
Facultative anaerobes have all the necessary components to do the above process
(enzymes, organelles, etc…), but when there is no O2 part of the system is turned off
(enzyme regulation).
Which part(s) would you hypothesize to be down regulated (turned down)?
The ETC obviously since there is no oxygen to accept the electrons at the end, but much of
Krebs too since it is partly used for stripping electrons from the acetyls and passing them
to the ETC…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
Evolution building on old systems
again: Glycolysis is universal to
both aerobes and anaerobes
(everyone does it!). All evidence
points to glycolysis being the first
to evolve for making ATP followed
by the addition of Krebs and the
ETC.
If glycolysis can make ATP, then why can’t facultative anaerobes just run
glycolysis? What is up with this fermentation?
Fig. 6.15A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
NAD+ must be
regenerated
The cell would quickly run out of NAD+ as all of it would be
converted to NADH, but NADH has nowhere to go since the
ETC is not up and running.
Fig. 6.15A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
Fermentation
- Performed by facultative anaerobes in the absence of
O2 to continue making ATP
- Krebs and ETC not used to make ATP
- Two types of fermentation
1. Alcohol (ethanol) fermentation
- Ex. Organism: yeast (single cell fungus)
2. Lactic acid fermentation
- Ex. Animal muscle cells and certain bacteria
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Facultative anaerobes
This is fermentation. It is glycolysis plus the regeneration of NAD+ so
that glycolysis can keep pumping out ATP for the cell. Specifically the
above is ethanol (alcohol) fermentation since ethanol is the product
after the oxidation and decarboxylation (removal of a carboxyl group,
which become CO2) of pyruvic acid.
Fig. 6.15A
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Fig. 9.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Beer and wine are made using yeast placed under anaerobic
conditions in the presence of grape extract or some kind of
malted grain like wheat/barley, respectively.
Fig. 6.15C
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
What if oxygen were to get into the vats?
Fig. 6.15C
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
How to make bread?
It is simple, you just need to add
flour, sugar, and yeast resulting in
dough. The oxygen in the dough will
be used up quickly and the yeast will
go anaerobic and perform
fermentation. The yeast will consume
the sugar producing CO2 (which causes
bread to rise and results in all those
bubbles inside the bread) and
ethanol, which evaporates during the
baking process.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
How about lactic acid fermentation?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Another form of fermentation is shown above where instead of ethanol
being produced from pyruvate, lactic acid is produced. The purpose it
the same, regenerate NAD+ so that glycolysis can keep going and ATP
can keep being made. Notice that decarboxylation does NOT occur here
as lactic acid still has three carbons like pyruvate. This is only a redox.
Fig. 6.15B
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
2. LACTIC ACID FERMENTATION
Fig. 6.15B
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
2. LACTIC ACID FERMENTATION
Fig. 9.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Yogurt is made using lactic acid fermentation by the bacterium
Lactobacillus acidophilus. Just take some milk, add the bacterium and
seal it to prevent O2 from getting in. Let is stand for some time and
then add your favorite flavoring.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
When we contract our muscle cells over and over, the oxygen gets used up quicker than it
can be brought from your lungs via the bloodstream. This causes the cells to switch to
lactic acid fermentation to make ATP. The lactic acid is secreted from the cells into your
blood and picked up by the liver cells to be converted into glucose by gluconeogenesis –
almost the reverse of glycolysis - and the glucose is stored as glycogen.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Lactic Acidosis – a disease characterized by too much lactic
acid in the blood. Could be caused by severe liver damage
or a number of other deficiencies. Lactic acid is obviously
an acid and your blood becomes acidic resulting in deep and
rapid breathing.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Why don’t we
do ethanol
fermentation ?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: How do cells make ATP in the absence of O2?
Summary:
(fermentation)
or ethanol depending on organism
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Who goes around eating
monomers of glucose?
nobody
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
We eat organisms or substances made by organisms like milk.
These are complex mixtures of assorted carbohydrate, protein
(polypeptide), and nucleic acid polymers of various length,
lipids, vitamins, minerals and many other metabolic compounds
(substrates, products, intermediates).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
Peanuts are composed predominantly of assorted polysaccharides,
triglycerides (fats) and proteins excluding the vitamins and
minerals. What will happen to all of these polymers in your
gastrointestinal (GI) tract (digestive system)?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
monosaccharides
The polymers and triglycerides will be broken down to
monomers and fat components, respectively. What is the fate of
these monomers/components in your cells?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
monosaccharides
They can directly be used for biosynthesis, they can be stored
or…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
…the monomers/components can enter cell respiration at
various stages and be burned for ATP or used to make other
monomers/components:
1. Glycerol can be converted by enzymes to G3P.
2. Fatty acids can be converted by enzymes to many acetyl CoA in peroxisomes by β-oxidation.
3. monosaccharides will enter glycolysis
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
β-oxidation
Breakdown of fatty acids into
acetyl CoA molecules.
Ex. If the fatty acid has 16 carbons, 8
acetyl CoA can be made and funneled into
grooming.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
3. Amino acids can be deaminated (the amino group removed). The amino
group is waste and will be converted by enzymes to urea, which is part of
your urine (it is excreted). The remaining part of the amino acid can be
converted to intermediates of krebs cycle, acetyl coA or pyruvic acid and
burned or used to make other monomes, all by enzymes of course.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
In the end, all the pieces can be burned (electrons held by C and H are
removed and passed to oxygen) to make ATP with the exception of the
amino groups of amino acids.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 6.16
Reminder: These are all catabolic (breaking down) reactions that are
overall exergonic in nature. Also, just in case you didn’t put it together
yet, this is all metabolism (chemical reactions in the cell).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Fig. 9.19
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What will some of the ATP be used for ?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
What will some of the ATP be used for ?
biosynthesis
(anabolic reactions)
Other uses we have scene thus far: vesicle transport (motor proteins that carries vesicles use ATP), active transport,
muscle contraction, etc…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Biosynthesis
Krebs cycle intermediates, acetyl CoA, pyruvic acid and G3P (PGAL) can all
be used to make monomers, which in turn will make polymers.
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Biosynthesis
1. Pyruvic acid can be converted back into G3P and in turn into glucose
(the reverse of glycolysis…almost…called gluconeogenesis).
Gluco = glucose
Neo = new
Genesis = origin (creation)
=
creation of new glucose
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Of course, glucose can then be combined to make polysaccharides…
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
2. Kreb cycle intermediates, acetyl CoA, and pyruvic acid can be used, in
combination with amino groups, to make...
amino acids
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
This diagram shows OAA (oxaloacetate), a Krebs intermediate, being
converted into the amino acid aspratate, which can then be converted to
the amino acid asparagine; all by enzymes of course. Therefore if you do
not eat these amino acids directly, you can always make them.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
This diagram shows α-ketoglutarate, another Krebs intermediate, being
converted into the amino acid glutamate, which can then be converted to
the amino acid glutamine through an intermediate; all by enzymes of
course.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Humans can make 12 of the amino acids (called the non-essential amino
acids). The other 8 are essential amino acids (you must get them in your
diet, you cannot make them).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Of course the amino acids are going to be used to make…
polypeptides
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Of course the amino acids are going to be used to make…
polypeptides
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Reminder: Ribosome, made of
rRNA and proteins, randomly
bumps into and binds mRNA.
tRNA brings the amino acids to
the ribosome according to the
mRNA sequence (codons).
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
How can triglycerides be made?
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
3. Acetyl CoA can be used to make fatty acids, while G3P can be used to
make glycerol. The fatty acids and glycerol can combine to make
triglycerides (fat).
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
These are the reactions of fatty acid
synthesis in the smooth ER. Just like
any enzyme pathway, multiple
different enzymes work together
like a factory line to make
(anabolic) or break (catabolic)
molecules.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Of course, the
polymers are used to
build and maintain
cells, to signal cells
(hormones), etc…
Fig. 6.17
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Why break down the monomers just to
remake them again????
They are not the monomers you need at that moment (regulation by
negative feedback). See next slide…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
For example, what if you have not eaten the amino acid
serine in a while and your cells are running low, but you
have tons of alanine?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
For example, what if you have not eaten the amino acid
serine in a while and your cells are running low, but you
have tons of alanine?
Take the alanine, convert it to a Krebs cycle intermediate, take the
intermediate, and synthesize the serine from it…
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
How can a person gain weight in the form of
stored fat if they only eat carbohydrates ?
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
How can a person gain weight in the form of
stored fat if they only eat carbohydrates ?
Carbs are broken into monomers like glucose, which are converted to G3P. Some of the G3P will be
converted to acetyl CoA. Now you have both G3P and acetyl CoA. G3P can then be converted to
glycerol. The acetyl CoA can be converted to fatty acids. Combine the glycerol and fatty acids to
make triglycerides.
Chapter 9 - Cell Resp: Harvesting Chemical Energy
AIM: Describe the process and purpose of cell respiration
Q. Which can make more ATP, a glucose or a
triglyceride?
THE FATE OF FOOD
1. Cellular respiration
-break down food
- Generate intermediates
and ATP
Exergonic
Powers
Endergonic
2. Biosynthesis
-Use ATP and intermediates
-Build raw materials not found
in food or that you have not
eaten in a while.
3. Storage to do 1 and 2 at a
later date